We studied the crystallographic features, especially the orientation relationship with respect to austenite, of martensite in a steel transformed from coarse-grained equiaxed austenite (35 μm), ultrafine-grained equiaxed (2.5 μm) or lamellar (300nm) austenite fabricated by sever plastic deformation. With decreasing the grain size of equiaxed austenite, the orientation relationship changed from Kurdjumov - Sachs relationship to Greninger - Troiano relationship. We inferred that this change of orientation relationship could be attributed to the small size of martensite plate transformed from the ultrafine-grained equiaxed austenite. The martensite transformed from the ultrafine-grained lamellar austenite did not have a definite orientation relationship with austenite. We considered that a high density of dislocations or a high density of low angle boundaries within the ultrafine lamellar austenite grain resulted in the large deviation of orientation relationship.